An Imported Disease Is Threatening Seattle's Local Bat Population

A brown bat like this one was found dead in 2017, infected with a fungus that has decimated bat populations on the East Coast. Protecting the species helps control insect populations; these bats consume up to twice their body weight in one evening. Photo by Igor Cheri

In April 2017, Chris Anderson, a biologist for the Washington Department of Fish and Wildlife (WDFW), received a call from a wildlife rehabilitation facility. A hiker had called about a dead bat he’d spotted on a trail near North Bend. Anderson has a broad job description: He’s in charge of studying and managing King County fauna ranging from insects to elk. But he has wildlife favorites, and the longer he’s been on the job, the more he’s become intrigued by bats. “They are so smart, they’re long-lived and they each have unique characters,” he says. Anderson compares their personalities to those of dogs or cats rather than to other wildlife he’s worked with.

The call about the dead bat made him nervous. That’s because local wildlife experts had recently made a troubling discovery: a sick bat, found not far from where this new bat sighting was located, that tested positive for Pseudogymnoascus destructans. This fungus causes white-nose syndrome, a disease so named because it frosts bat muzzles, wings and ears with the white fungus.

For more than 10 years, white-nose syndrome has spread rapidly through 30 states east of the Rockies and throughout eastern Canada, devastating many species of bats during hibernation. Entire caves on the East Coast that once held hibernating bats now hold nothing but heaps of bat bones—in some places, 10,000 or more bats in one cave have died. The disease has killed an estimated 85 percent of these hibernating bats. “Eighty-five percent of any critter, whether it’s bats or anything else, that’s a huge and potentially not recoverable impact to populations,” says Ann Froschauer of the U.S. Fish and Wildlife Service. She’s in charge of coordinating her agency’s white-nose syndrome response in Washington, Oregon and Idaho.

The fungus most likely came from Europe, although it doesn’t appear to have affected bats there, perhaps because they have evolved to coexist with it. It is believed to spread from bat to bat, or between bats and the surrounding environment. Humans who have inadvertently come in contact with the fungus (such as in a cave contaminated with white-nose) may also spread the disease by transporting spores on clothing or gear. That’s one of several theories about how this fungus has ended up in Washington state, but no one knows for sure how it got here.

Its presence here was especially surprising because the fungus had previously only been detected as far west as Lincoln, Nebraska, some 1,300 miles east. As of this spring, Texas is the only other western state besides Washington to report the disease.

A DISEASE ARRIVES: White-nose syndrome arrived in Washington state with this bat. Photo courtesy PAWS

While white-nose syndrome has no health impact on humans, we will feel its effects as it ravages bat populations. While some bats in the world eat fruit, others drink nectar, and three bat species (the “vampire” bats that make humans squeamish) lick up blood. Northwest bats are insectivores, as are most bats in North America. These pest control dynamos can consume twice their body weight in insects in one evening, ridding patios and parks of mosquitoes, flies and other insects humans dislike.

No one has yet quantified how many bug bites have been prevented by bats, but researchers have begun to enumerate how bats help U.S. agricultural crops, including corn, pecans and cotton, by eating pests that plague them. Early studies show that value to be more than $20 billion annually in pest control savings. Here in Washington, fruit growers are paying attention to the arrival of white-nose, says Anderson. “I’ve gotten lots of calls from orchardists asking how they can support bats,” he says. “They get it.” So should city dwellers who buy cotton, corn, pecans and apples and don’t want to pay more for them. Tequila drinkers might also raise a shot glass to the bat species in Mexico that is the primary pollinator of the agave plant, the source of tequila and mezcal. That bat, which is not threatened with white-nose, was recently removed from the endangered species list, but another bat species, the northern long-eared bat, was listed in 2015 as threatened directly by the effects of white-nose.

White-nose syndrome takes advantage of the vulnerability of bats during hibernation. Bats rest during the day and forage at night, and many bats also hibernate for several months in places with cold winters and few insects, such as along much of the East Coast of the United States and, in some cases, here in the Northwest. Other bats migrate in winter or, in warm climates, stay active year-round. Some bats hibernate alone, but others cluster for months in places with high humidity and temperatures between 34 and 41 degrees Fahrenheit, temperatures found in caves, mines, talus slopes or other rock crevices. White-nose thrives in just these conditions.

During hibernation, the mammals slow their heart rates from 200–300 beats per minute to 10 beats per minute, lower their body temperature and slow other body functions to save energy. When the fungus takes hold, it wakes the bats, causing them to lose fat reserves at a time when there are no insects to replenish them. The disease also damages wings, affects body temperature regulation and causes dehydration. Scientists aren’t sure if species that don’t hibernate, such as some migratory bats, are affected by the disease.

Froschauer says some eastern bat populations are unlikely to recover for several generations, given the slow reproduction of bats (some species only give birth to one offspring a year) and the fact that the fungus tends to persist once it takes hold at a site. Some species may go extinct.

With general details about the location of the tiny bat spotted by the hiker, Anderson painstakingly walked the landscape until he found it. He plucked it up with rubber gloves and identified it as a Yuma myotis, a bat less than 2 inches long, no heavier than a quarter, with fuzzy light brown fur. He noticed ominous signs that could indicate white-nose. Bats have leathery, somewhat wrinkly wings, but these wings were different, he says—“puckery, like seersucker fabric.” They also appeared shrunken in places where wings should spread out.

The biologist placed the bat in a special container and returned to his truck. There, to avoid spreading the disease, he changed into extra clothing he’d brought, crammed what he had been wearing into a special bag for decontamination and sprayed his equipment with special chemicals.

Lab tests on the bat soon confirmed white-nose—the second case in the state. When the news came to the WDFW offices, Anderson said, “You could feel it in the room—we were just…a bit heavy.” Their concern was well founded. Within a year, more bats with the fungus had been found in King County, and it appeared to be spreading: In May 2017, the National Park Service swabbed 24 live bats in a roosting area in Mount Rainier National Park, finding four that carried the fungus. None of the 24 bats showed signs of the disease—a good sign, given that some species back east have remained unharmed. Perhaps these would, too. No one knows how many more Washington bats may be infected. “It’s very plausible that there are a lot of other individuals that are dying on the landscape and we’re just not finding them,” says Anderson.

There is currently no treatment for white-nose that can counteract this trend. Researchers have figured out ways to kill the fungus, including using ultraviolet light, but it’s one thing to wipe it out in a lab, and quite another to apply treatments in the field without harming the animals or inadvertently undermining an entire ecosystem.

Photograph by: Hayley Young (anderson); Biologist Chris Anderson holds a “bat detector” which helps locate live bats; he’s in an area near North Bend where he followed a lead to discover a dead bat infected with white-nose syndrome.

One complicating factor in tracking white-nose in Washington state is that scientists here don’t know where most local bats spend the winter. Some of the bats, they suspect, don’t hibernate at all, while larger species, such as the hoary bat, migrate south to California for the winter. There are few known bat caves in our state, unlike the many large caves known in other regions, such as Mammoth Cave in Kentucky and Howe Caverns in Albany, New York, where the first U.S. cases of white-nose were discovered. That’s where scientists have focused much of their work on white-nose.

“Surveillance work to track disease and monitoring work on bats can be a little more difficult in western landscapes, given that they’re so vast and there’s so much roosting variation,” says Abby Tobin, who coordinates white-nose efforts for the Washington Department of Fish and Wildlife.

The other problem is that the American public has traditionally been wary of bats, equating them to blood suckers, rabies vectors and hair entanglers. The public doesn’t think of them as bug eaters, pollinators and arguably adorable fellow mammals.

Some Seattleites have tried to change that image in recent years. “When I got interested in bats in the late 1960s, they were still considered vermin—they were in the category with starlings and English sparrows,” says John Bassett, a retired research scientist in environmental physiology at the University of Washington who, with others at the nonprofit organization Bats Northwest, helps lead summer bat walks and conduct bat studies.

And the facts about bats are fascinating. There are 15 known bat species in Washington state and 11 in the Puget Sound area, but it’s possible there are more species that haven’t been located yet. Washington state species range in size from the canyon bat (also known as the western pipistrelle), with a body no bigger than a matchbox, to the hoary bat, which is the size of a small mouse. A number of our species are distinct to the West Coast.

As fellow mammals, bats are warm-blooded and nurse their young. They’re in the mammalian order Chiroptera, which means “hand wing” in Latin, so named because their wings are different from bird wings and similar to human hands, formed with four elongated bones that are held together by a thin membrane, and one thumb. In the city, says Bassett, bats are all around, but we don’t notice them because they spend their days roosting in warm places, such as attics, sheds, the undersides of some bridges, in old trees with woodpecker holes or, for the smallest bats, tucked under the cracking bark of old trees.

Bats Northwest is working with state, federal and nongovernmental agencies in a coordinated effort to learn more about local bats and confirm baseline information, such as estimates of species populations for Washington bats. Among other strategies, these organizations are doing acoustic monitoring, using specialized recording equipment to listen in on bat echolocation calls, which are outside the range of human hearing. Aside from expanding general knowledge about local bats, this information could also help better track the white-nose fungus.

Meanwhile, says Fish and Wildlife’s Froschauer, there’s unlikely to be a “silver bullet” for saving at-risk bat species. Instead, a combination of things is needed, including providing habitat that gives bats safe places to roost, forage and raise young. Fattening up bats before hibernation “may help them hold longer if they do get the disease,” she says. “Bats can survive the disease; if they emerge and get food and water, they can recover,” she says.

Back east, some members of species plagued by the disease are doing just that. “They are surviving through this disease and managing to reproduce, so that’s a glimmer of hope,” says Froschauer.

For the moment, western Washington still has plenty of bats, snoozing, reproducing, raising young and gorging on bugs. They are also going largely unnoticed—although not always. Bassett once received an email, with photos attached, sent by a family that had been picnicking under an oak tree in Seward Park. They looked up to see a family of bats: a mother hoary bat hanging with her three babies. She sported fluffy, tricolored fur—“one of the prettiest of all bat species,” says Bassett. The bats are here, he says. “It’s just a matter of looking.”

Now, more than ever, researchers hope people will do just that.

***

What to do if you spot a bat

If you know of groups of bats—a regular roost or a maternity site, or if you know about bats in winter or see bats flying during the day—you can report your observations to the Washington Department of Fish and Wildlife (WDFW) at 360.902.2515 or go to wdfw.wa.gov/bats. Also contact the WDFW if you find a dead bat.

If you are bitten or scratched by a bat, contact the Seattle & King County Public Health department at 206.296.0100. Never handle a bat, dead or alive. Bats can be infected with rabies (though less than 1 percent are); last summer, three bats infected with the disease were found in the Seattle area in August.

To help with bat conservation, avoid entering areas where bats may be living to limit the potential of transmitting the white-nose syndrome to other areas. Do not allow pets or other domestic animals to access areas where bats may be roosting or hibernating as they may act as carriers of the fungus. Avoid disturbing bats when possible. Consider providing bat habitat in the form of hollow trees and snags, or a bat box (find details at batsnorthwest.org).

Learn MoreBy Sarah Edwards

Bats Northwest has a variety of educational programs and offers bat walks at Green Lake, including one at 6:30 p.m. on September 10. For more details, go to batsnorthwest.org.Bats About Our Town, in Olympia (batsaboutourtown.com), offers information for self-guided bat walks and general information about bats. From May through September, at least five species of bats are known to feed on insects over Capitol Lake in the center of Olympia.The Seward Park Audubon Center (Seward Park, 5902 Lake Washington Blvd. S; 206.652.2444) occasionally offers guided bat walks to locate and identify these mammals in their natural habitat. Check website for information.

Related Content

The West Seattle Bridge may not be open until 2021; the Farmers Markets are starting to come back, and the Tulip festival would like you to stay home, please. All the news you missed in between reading about coronavirus.